1. Field of the Invention
The present invention relates to an article pickup apparatus and an article pickup method for recognizing a position and a posture of an article randomly piled in a three-dimensional space and for picking up the recognized article using a robot.
2. Description of the Related Art
As an apparatus of this type, conventionally, there is known an apparatus configured to recognize a position of an article by applying pattern matching to a two-dimensional image obtained by imaging articles randomly piled using a camera or a three-dimensional point set obtained by measurement using a three-dimensional measurement instrument. Such an apparatus is described, for example, in Japanese Laid-open Patent Publication No. 2004-295223 (JP2004-295223A) and Japanese Laid-open Patent Publication No. 2011-179909 (JP2011-179909A). Further, an apparatus configured to calculate a three-dimensional posture of a rotating body using two images obtained by stereoscopic photography is also known. This apparatus is described, for example, in Japanese Laid-open Patent Publication No. 2011-022084 (JP2011-022084A).
In the apparatus described in JP2004-295223A, a two-dimensional model pattern is previously prepared from a two-dimensional image obtained by imaging an article having a standard three-dimensional relative posture, a plurality of transform two-dimensional model patterns are prepared by applying two-dimensional geometric transform to the two-dimensional model pattern, and two-dimensional pattern matching is applied to a two-dimensional image of an article using the plurality of transform two-dimensional model patterns.
In the apparatus described in JP2011-179909A, while a three-dimensional model pattern of an article is previously acquired from a CAD model or the like, surfaces of articles in a three-dimensional space are measured using a three-dimensional measurement instrument and a three-dimensional point set (an distance image) is acquired, and then the three-dimensional point set is divided into partial regions surrounded by an edge extracted from the three-dimensional point set. Then, initially, one of the partial regions is set as an article region, and both matching processing of the three-dimensional model pattern for the article region and update processing for adding another partial region to the article region are repeated to measure positions and postures of the articles.
In the apparatus described in JP2011-022084A, using a pair of cameras, a pair of images are acquired by imaging a rotating body from different directions, a center axis of the rotating body is set by calculating a main component axis of the rotating body via main component analysis with respect to each pair of images, and three-dimensional information of the center axis is determined based on the principle of triangulation using a pair of images to calculate a posture of the rotating body.
However, in the apparatuses described in JP2004-295223A and JP2011-179909A, it is necessary to previously prepare a two-dimensional model pattern or a three-dimensional model pattern for each kind of article, and therefore, time and effort are needed. Further, in the apparatus described in JP2011-022084A, a posture of a rotating body is calculated using two images stereoscopically photographed and therefore, a pair of cameras needs to be provided, resulting in a large-scale apparatus configuration.